Four new resin glycosides, calyjaponins I-IV, from the aerial parts of Calystegia japonica.

Calystegia japonica Choisy (Convolvulaceae) is a perennial herbaceous vine widely distributed throughout southeastern and eastern Asia. In traditional Chinese medicine, the whole parts of C. japonica have been used for their diuretic and tonic properties. In this study, four new resin glycosides, designated calyjaponins I (1)-IV (4), were isolated from the aerial parts of C. japonica. Their structures were elucidated on the basis of spectroscopic data and chemical analyses. All compounds possessed new glycosidic acid moieties and were identified as hexaglycosides featuring intramolecular cyclic ester (jalapin-type) structures, in which the sugar moieties were partially acylated with organic acids, including (E)-2-methylbut-2-enoic and 2R-methyl-3R-hydroxybutyric acids. Compounds 1-4 were further evaluated for antiviral activity against herpes simplex virus type 1 (HSV-1) and for cytotoxicity against HL-60 human promyelocytic leukemia cells. All tested compounds exhibited both anti-HSV-1 and cytotoxic activities.